Endocrine Abstracts

Introduction: C1q/TNF-related protein-3 (CTRP-3) is a newly discovered adipokine with anti-inflammatory impact on monocytes by down-regulation of pro-inflammatory cytokines, e.g. interleukine 6 (IL6) and tumor necrosis factor alpha (TNF-alpha), in both adipocytes and monocytes. So far it is unclear which kind of interactions and molecular mechanisms are underlying the observed effects. Our aim is to characterize the differential effects of the globular and the collagenous domain of CTRP-3 and to compare these with the effects exerted by the full length protein.

Methods: DNA of recombinant full-length CTRP-3, its globular domain, and its collagen domain were transfected into and expressed in H5 insect cells. The secreted proteins were extracted from the cell culture supernatant and purified by affinity chromatography.

Costimulation experiments were performed in 3T3-L1 and monocyte-like THP-1 cells with pro-inflammatory stimuli lipopolysaccharide (LPS) and free fatty acids (FFA) plus CTRP-3 or its globular domain, respectively. Gene expression and secretion of pro-inflammatory cytokines were measured by real time RT-PCR and ELISA techniques. Protein levels of intracellular components of pro-inflammatory signaling were analysed by Western blot.

Results: Both full-length CTRP-3 and its globular domain were shown to decrease the amount of secreted IL6, MCP-1 and resistin after costimulation with LPS and FFA in differentiated 3T3-L1 cells. RT-PCR results confirmed down-regulation of these pro-inflammatory factors on mRNA level. Decrease of secreted IL6 in THP-1 cells upon costimulation with LPS and CTRP-3 globular domain could be shown as well.

Conclusion and outlook: The results suggest that the observed anti-inflammatory impact of CTRP-3 is mediated by its globular domain, whereas the collagen like domain is still to be tested on these effects. As a next step we plan to investigate the anti-inflammatory effects of CTRP-3 in an animal model of LPS-induced SIRS.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.